Method and apparatus for the transmission of pictures and views



Nov. 8, 1927.

C. A. HOXIE METHOD AND APPARATUS FOR THE TRANSMISSION OF PICTURES AND VIEWS Filed Sept. 23. 1924 5 Sheets-$heet 1 Inventor: Charles A. Hoxie.

HIS Attorneg.

Nov. 8, 1927.

C. A. HOXIE METHOD AND APPARATUS FOR THE TRANSMISSION OF PICTURES AND VIEWS Filed Sept. 23, 1924 5 Sheets-Sheet 2 Fig. 2.

QM e A15 w r m n m ms t e A N I .6. ZN C Nov. 8, 1927. 1,648,687 c. A. .IHOXIE METHODAND APPARATUS FOR THE TRANSMISSION OF PICTURES AND VIEWS 5 Sheets-She et s i llllll l l'l l l s Ihventor: 3 Charles A.Hoxie,

V y M HIS Attorney.

Nov. 8, 1927. 1,648,687

c. A. HOXIE METHOD AND APPARATUS FOR THE TRANSMISSION OF PICTURES AND VIEWS Filed Sent. 25. 1924 5 Sheets-Sheet 4 Fig. 8.

Inventor: Charles A. Hoxie.

by y; HIS Attorneg Nov. 8, I927.

. C. A. HOXIE METHOD AND APPARATUS FOR THE TRANSMISSION OF PICTURES AND vmws Filed Sept. '23. 1924 Patented Nov. 8, 1927 UNITED STATES 1,648,687 PATENT OFFICE.

. l CHARLES A. HOXIE, O1 SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

METHOD AND APPARATUS FOR THE TRANSMISSION 01 PICTURES AND VIEWS.

Application filed September 23, 1924. Serial No. 739,423.

My invention relates to the electrical transmission of pictures and views by wire or by radio, and an object of my invention is the provision of an improved method and means for this purpose.

My invention will be better understood from the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims. Certain features described herein are claimed in a copending divisional appli-. cat-ion Serial No. 177,684, filed March 23,

In the drawing, Fig. 1 is a perspective 1 representation and circuit diagram of one form of sending apparatus involving my invention; Fig. 2 is a similiar representation of one form of receiving apparatus; Fig. 3 shows a modification of Fig. 2; Fig. 4 shows another modification of sending and receiving apparatus; Figs. 5 and 6 are details showing the effect of the vibration of the light beam of the receiving apparatus of Fig. 4; Fig. 7 shows a modified form of the sending apparatus shown in Fig.4; Figs. 8 and 9 show further modified forms of sending ap paratus; Fig. 10 shows a form of sending ap paratus for transmitting motion pictures from a motion picture film; Figs. 11 and 12 show two forms of sending apparatus for transmitting pictures of moving objects or of moving images thereof; Figs. 13 and 14 show two forms of apparatus whereby moving pictures may be received and directly 5 observed during the reception; Fig. 15 is a detail showing a modification of. the apparatus shown in Figs. 13 and 14, Fig. 16 is a fragmentary View on a greatly enlarged scale of a screen adapted to take the place of the rotatable chopper of Figs. 1. 10 and 11. and Fig. 17 shows the screen 189 as applied to the arrangement of Fig. 1.

Referring first to Fig. 1 where the apparatus is shown in a moreor less diagrammatic form tor convenience in illustrating the parts, the picture to be transmitted, which in this case is a transparency, is represented at 1. Lightfrom a lamp 2 passing throughthe picture is brought to a focus by a lens or lens'es adjustably mounted in a tube 3. The plane of the image thus formed 'is between the stationary mask 4 and the movable apron 5. The mask4 has anopening 6 therein and" directly behind this opening is a photoselectric cell 7 having a window 8 facing the opening 6, with the window and the opening being somewhat larger than the aforesaid image of the picture to be trans mitted. Rigidly secured to, a lower or base plate 10 and an upper plate 11 are three screw-threaded rods 12, 13 and 14, the upper and lower iportions of rods 12' and 13 being smooth to orm guides for fingers 15 and 16 of the apron 5. On the screw-threaded portion of each of rods 12 and 13 is mounted a 6 threaded pulley 18 and two pairs of fingers 19 on the apron 5,embrace these pulleys in the manner illustrated, whereby as the pulleys are turned the apron is raised or lowered. The driving belt 20 passes around 7 the two pulleys 18 and around a third threaded pulley mounted on the rod 14 which latter pulley is secured to a splined screwthreaded sleeve 21 rotatably mounted in a bracket 22. The worm gear 24 splined to the sleeve 21 is inimesh with the worm 25 on the shaft of the driving motor 26. For the purpose of preventing slippage of the belt the pulleys are shown provided with teeth 27 which engage in suitable openings 30 28 in the belt. At distances along the belt corresponding approximately to the length of the image of the picture to be transmitted are small openings 30 all at the same distance from one edge of the belt and equally spaced. Opposite the openings 30 in the belt is an elongated opening 31 in the apron 5 having a width somewhat greater than the openings 30 and having a length at least as great as the corresponding dimension of the no image. Between this opening 31 in the apron andthe tube 3 is the chopper 32 which may be a toothed wheel or, as shown on the drawing, may be a transparent disk having opaque radial lines drawn thereon. 05 The wheel 32 is driven by an electric motor 33 at a proper speed to produce a carrier wave having a suitable freqruency.

The photo-electric cell is shown connected in a circuit including a battery 36 and a resistance. 37 The variations in the potential drop across this resistance due to the variations in the amount of light entering the cell 7 are amplified by means ofthe pliotron 38 of which the grid 39 is connected with one end of the resistance 37 and the filament 40 is connected with the other end. The plate 41 is in circuit with the primary 42 of a transformer and the battery 43. The I secondary 44 of this transformer is shown connected to the wires which ma comprise a metallic or grounded circuit eading to the receiving apparatus or may be suitably connected with radio transmitting apparatus for radio transmission. It will be obvious that if greater amplification is desired, a plurality of pliotrons suitably connected together may be used instead of the single pliotron illustrated.

For the purpose of synchronizing the sending and receiving apparatus, an alternating current'generator 4 isshown directly connected to the driving motor 26. The current from this generator may be a relatively low frequency, for example sixty cycles, and after passing the transformer 48 is applied to the wires 45 and the impulses transmitted to the receiving station by the same means by which are transmitted the impulses originating at the photo-electric cell.

The operation is as follows: With the transparency 1 in position the lens tube 3 is adjusted to produce a sharp image of the picture in the plane of the belt 20. The chopper wheel 32 is rotated in the path of the rays so as to interrupt the rays at a suitable radio frequency. belt 20 and screw pulleys over which it runs are brought to either their uppermostor lowermost position. For example, we shall assume the belt is started at its lowermost position at which the holes 30 are in line with the lower edge of the image. Motor 26 being started drives the generator 47 and'drives the belt 20. As

the pulleys carrying the belt slowly travel upwardly on the stationary threaded rods 12, 13 and 14, the openings 30 pass in suc- 'c'ession across the image each opening 30 traversing the image on a path. slightly above that of the preceding opening until the entire image has been covered. Since the spacing of the openings 30 is such that only one openmg'is traversing the image at any one time, it will be seen that the-amount of light passing into the photo-electric cell is constantly varying in accordance with the high lights and shadows ofthe image in the path of the opening. At the same time the chopper 32 interrupts the passage of light with a uniform high frequency the resulting voltage waves applied by the transformer secondary 44 to the wires 45 will have a high frequency and the envelope of these waves will vary in am litude in accordance with the intensity of hght at the elemental portions of the image as determined by the openings 30 in the belt. The low frequency voltage applied to the wires 45 from trans- ,former 48 will always be in exact synchronism with the movement of the openings 30. While I have chosen to illustrate the picture to be transmitted as a transparency, obvious-. 'ly it'may be an ordinary picture well illuminated 'or simply a view.

As illustrative of how the transmitted im-' wires 51 which may connect directly with the wires 45 of-Fig. 1 or may connect with suitable radio receiving apparatus (not shown) lead to a pliotron amplifier 52 the plate of which in turn connects with the terminal of a transformer 53. The secondaryof this transformer is shown connected with the terminals of the discharge lamp 54 having a pair of electrodes 55 spaced a art at the neck of a tube containing a gas, {Ear example by which a light is produced which is strongly-actinic. For tuning purposes a variable condenser 56 is bridged across the transformer secondary. Light from the lamp 54 is brought to a focus by a suitable lens 57 and passes through a small opening, for example, of the same size as the o enings 30 with belt, in the casing 58 enc osing the photo-sensitive receiving surface 59. This surface is shown carried by the drum 60 which is rigidly secured to the sleeve 61 passing up through the bottom of the casing 58 and having a bearing on the supports 62.

Sleeve 61 is internally screw-threaded to'engage with the threaded stationary rod 63 and is externally splined at 64 to receive a sliding key on the worm gear 65. In mesh with this worm gear is the worm 66 shown on the shaft of the electric motor 67. The circuit of this'motor connects with the sec ondary of the transformer 69, the primary of which is in the plate circuit of the amplify-' ted and having a frequency determined by the chopper 32 and another, a synchronizlng wave, of co ns'tant amplitude, preferably of some lower frequency, as for example, 60 cycles produced by the generator 47. By means of the variable 0 ndensers 56 and 71 the circuits of the lam 54 and the motor 67 may be tuned to the respective frequencies produced by the chopper and the generator. The brightness of discharge lamp 54 will thereby vary in accordance with the high lights and shadows of the image being passed over by the openings 30 in the belt 20. The drum 60 carrying the sensitized film 59 1s rotated by the motor 671 so as to "make one complete rotation in the time required for the belt 20 to move the distance between two successive openings 30. The drum 60 in rotating travels vertically at the same speed as the vertical movement of the belt, so that when the filmforming the sensitive surface 59 covering the drum is removed and developed an exact reproduction is obtained of the original transparency with the exception that if the original is a negative the reproduction will be a positive and vice versa. 7 The transparency 1 to be transmittcd may of course be placed in position before the lamp 2 either erect or inverted, direct or reversed. Whether or not the picture as it is being reproduced is erect or. in verted, or direct or reversed obviously depends upon whether the drum travels upwards by. or downwardly on the screw 03 or is rotated to the right or left.

The modification shownv in Fig. 3 differs from that of Fig. 2 only in that the lens 57 is dispensed with and the discharge lamp is bent at its neck or light emitting portion arranged close to the opening in the casing 58.

In the modified form of transmitter andreceiver shown in Fig. 4 the'transparency comprising the picture to be transmitted is wrapped around a transparent drum within which is located the photo-electric cell 81. The drumis mounted to rotate and to feed slowly upward or downward 'just'as in Fig. 2,the power being supplied by the motor 82 on the shaft of which is the disk 83 having a 'row of perforations 84 arranged around its periphery. Light from a suitable source 85 passes through these perforations in succession and is focused by the lens 86 on to the small opening 87 in the enclosing casing 88 from where it passes through the transparency into-the window of the photocell 81. The perforated disk 83 thus acts as a chopper and functions like the chopper-31 of Fig.- 1 to produce a carrier wave having the desired frequency. The same disk 83 is used in this modification to give the synchronizing wave. The light from a. lamp 89 similar to lamp 85 extends through a row row openings 90 which, for example, may be half the number of the openings 84 through lens 91 and into the window of a second photo-electric cell 92. The circuits of the two cells 81 and 92, the amplifying pliotrons 93 and 94 and the transformers 95 and 96 are similar to the corresponding partsshown in Fig. 1. The line wires 97. and 98 may connect together directly the transmitter and receiver or may connect-with suitableradio transmitting and receiving apparatus as stated above in connection with Fig. 1.

Referring now to the receiving apparatus illustrated in Fig. 4, the wires 97 and 98 are Y ture is attached to a rodk a; small mirror 108. This shaft and mirror shown connected to pliotron amplifiers 100 and 101 and to transformers 102 and 103 having tuning condensers 104 and 105 similar to those illustrated in Fig. 1.

The secondary of transformer 102 connects with an electroma net 106 whose armashaft- 107 carrying are shown in my Patent No. 1,456,595 May 29, 1923. The armature of electromagnet 106 may have the form of a circular diaphragm instead of the form illustrated in that patent. Light from a suitable lamp 109 having a line filament passes through the lens 110 to the mirror 108 from whence it is reflected back through the same lens to a cylindrical lens 111 by which the line image of the filament is contracted to a spot which passes through the opening 112 in the casing 113. Within this casing is the drum 114 around which a sensitized strip or film is adapted to be placed. The drum is mounted in a manner similar to the drum 80, whereby as it is rotated it feeds up or down at the same rate as drum 80. The synchronous driving motor 115 is supplied from the transformer 103 and connects with the drum. through worm gearing as shown. In order that the receiving drum 114 may be automatically started at the proper time after the motor has been started and when transmission of the picture is to begin, a contact device 117 in the primary circuit of transformer 96 is adapted to be opened by the baggage of a pin 118 on the drum 80. An impulse is thereby sent which by apparatus now to be described serves to start the rece ving drum. A clutch 119 in the motor drive shaft is normally held closed by the spring 120] At starting the clutch may be held open by a lever 121 and latch 122. The electromagnet 123 which is in series with the motor 115 responds to the impulse originating at the sending station and releases the latch whence the receiving drum starts rotating.

In this modification, the frequency of the carrier wave for the picture is determined by the rate of passage of the openings 84 in the disk 83. Its amplitude is constantly being varied by those light and dark portions of the picture being transmitted which lie in the part of the light beam entering the opening 87. The carrier wave for synchronization of the receiving apparatus is not modulated but has a constant frequency which is determined by the passage of the openings 90 and constant amplitude. At the receiving end the motor circuit is tuned to respond only to the lower frequency wave while the circuit of the electromagnet 106 is tuned to respond to the higher frequency wave. It will be seen that as the lamp 109 at the receiving station is located below the opening 112 inthe casing 113 and as the shaft 107 rocks on a horizontal axis, vibrations of the mirror-108 cause the reflected" light beam toform a vertical illuminated streak on the casing 113 extending through in Fig.

-tions 128 correspond toportions 126.

5. Here, the darkest or most ex-' posed portions 125 -correspond to the times of minimum vibratory movement light beam while the lightest or least exposed portions 126 correspond to the times of greatest vibratory. movement-of the beam. It will be remembered that the amplitude of the carrier wave is proportional to those portions of the high lights and'shadows of the pictures which lie in the path of the beam affecting the photo-electric cell. -By shielding the sensitive film on drum 114 from the vibrating beam through the small opening 112, an image resemblin what is shown in Fig. 6 may result where the dark portions 127 correspond to.

portions 125 of Fig. 5 and the lighter gera.- rious intermediate gradations ofcourse appear depending upon the amplitude of the vibration-of the light beam. I

In the modified form illustrated by Fig. 7 the synchronizing wave is produced by an alternating current generator direct connected to the motor 82 similar to the arrangement shown in Fig. 1, and the carrier ered during the reception of the picture.v

wave frequency is produced by a separate motor driven chopper 129 which serves to interrupt the light reaching the photo-electric cell.

In Fig. 8 I have shown a the receiving apparatus illustrated by Fig. 2 by which the picture may. be received on a flat surface instead of on. a drum. The

casing 130 having an elongated window 131' contains the flat sensitive surface which carries a rack 132 and is mounted for vertical movement. .The pinion which meshes wlth this rack is connected by suitable gearinglto t at the synchronous driving motor 133 so the sensitive surface is slowly raised or low- The disk 134 is rotated by the same motor and has a series of radially elongated peripheral openings 135 therein which successively pass the window131. Light in this case is shown coming from the discharge lamp 136 which after passing through the cylindrical lens-137 forms a bright band on the disk 134 opposite the window 131.- The motor 133 like the motor 6-7 ofFig. 2 will rotates.

'surface. v trated in Fig. 8 except that the source of 3 light is constant and the rays are vibrated operate in synchronism with the sending apparatus and will be so geared to the disk 134 that the successive openings 135 will pass the winding 131 at the same frequency as the openings 30 in belt 20 of Fig. 1 pass the photo-electric cell or with the same frequency with -which thedrum 80 of Fig. 4

In Fig. 9 I of the receiving apparatus shown by Fig. 4 by which the picture is received on a flat The apparatus is like that illusof the except what may pass.

modification of have illustrated a modification -in accordance with the received impulses as In Fig. 10 I have illustrated transmitting apparatus for sending motion pictures from a motion picture film. The picture film 145 passes from reel 146 up over the driving drum 147 to reel 148. Within the drum which is transparent is the photo-electric cell 149. In front of the drum 147 rotates the disk 150 having a series of openings 151 at equal distances from. the edge of the disk and equally spaced'apart at a distance substantially equal to the width of the film pictures. The disk is shown mounted on the shaft of the driving motor 152 to which is also connected by suitable gearing the shaft 153 by which the drum 147 is rotated. Light from the lamp 154 is concentrated by the.

lens 155 into a broad focal band on the disk 150 in the path of the openings 151 as they pass the film. Between the disk and the lens is the chopper 156 rotated at high speed by the motor 157. Unlike that in a moving picture machine, the film in this case moves witha unlform velocity and at the standard ratev of sixteen pictures per second. It will accordingly be seen that both'the disk 150' and the chopper 156 must-rotate at relatively high speed. The varying current from the photo-electric cell may be amplified and transmitted as in the form of my invention I already described. An alternating current generator 158 operated by motor 152 furnlshes the synchronizing wave for the receiving apparatus.

Instead of employing a lamp'giving a light of constant intensity and using a chopper to give the desired frequency the chopper may be dispensed with and a discharge lamp employed whichis fed from an alternating or pulsating source having the proper. freuency. I

In Fig. 11 I have shown an arrangement for transmitting directly from a moving object or from a moving picture. A disk 160 is shown as in Fig; 8 having a series of equally spaced openings 161, but in this case the openings. are arranged in a spiral path so that in one complete rotation of the disk the openings traverse every element of the picture. Light coming .directly from the moving ob ect or moving picture is brought to atoms by the lens 162 on the disk and "as the successive openings 161 pass this trol and the synchronizing means between disc arge lamps 170 operated by an alternating or pulsating current of a frequency corresponding to that obtained with the chopper of the previous form.

In Fig. 13, I have shown receiving apparatus wherebythe picture or view may be .observed directly, the disk 172 having a series of openings 17 3 arranged spirally as in the disk 160 is'rotated by the synchronous motor 174. In front of the disk is a relatively large collecting lens 175 before which is the discharge lamp 176 which is being energ'ized by the high frequency current received from the transmitting station and whose intensity of illumination is governed by the transmitting apparatus. Directly behind the disk is a light shield in the, form of a box-like enclosure 178 for excluding light and through which the image may be viewed by the observer.

Instead of viewing the image directly the image may be projected by a second lens 179 on a white screen 180 as illustrated by Fig.

14. The disk 172 of each of Figs. 13 and 14 in making one complete revolution covers the entire picture once. So also does each disk 145 of the transmitting apparatus shown in -Figs.'11 and 12, the corresponding disks of a transmitter and a receiver being similar in every way and operated at the same 'speed. In order to take advantage of the persistence of vision and to avoid flickering the discs should preferably make approxi-' mately sixteen revolutions per second. It should be noted however that where the transmitted image is observed by the operator the receiver may be driven by a substantially constant speed motor with hand conthe transmitter and the receiver dispensed with. In this case any variationin speed between the transmitter and the receiver would at once become apparent to the observer by the distortion of the picture but this could be corrected immediately by adjustm'ent of the speed of the receiving apparatu's. 1

In those forms of my invention where a rotatable disk is used having a spirally arranged row of openings as for example in Figs. 11, 12, 13 and 14, it'may be found that to accommodate a sufficientnumber of openings to give a picture which is not too,

coarse, the disk must be excessively large. In Fig. 15 I have shown how a smaller disk rotated at higher speed may be used by providing the same with several rows of openings. The disk 182 is here shown having openings 183 arranged in a'spiral which makes three turns instead of a single turn as before, the openings being arranged in radial alinement as shown. Cooperating with this disk is a rotatable screen 184 comprising a wheel having a cylindrical periphery provided'with axially elongated openings 185. Astationary screen 186 having a window 187 stands beside disk 182. The rotatable screen 184 is geared to the disk 182 and the rotatable screen openings are of such dimensions and so spaced that one disk opening only is. before a screen opening at any one time and as soon as light through one disk opening is cut off at one :end of a screen opening, light from the next disk opening enters at the opposite end of the same screen opening. In this manner the rotatable screen 184: shields the window 187 from all the disk openings except one at any one time. Within the rotatable screen 184: is shown a mirror 188 whichreflects the light laterally so that the image can be seen easily. When this arrangement is used in a transmitter, the mirror may be replaced by a photo-electric cell.

Instead of using a rotatable chopper, as for example in Fig. 1, to give the desired carrier wave frequency, I may use a stationary finely ruled screen or a fine grating. In Flg. 16 I have shown a fragment of such a screen or grating at 189 drawn to a greatly enlarged scale in which the transparent portions 190 are somewhat wider than the opaque portions 191. The width of the latter portions may be approximately equal to disks of those figures. It will thus be seen that in each case the light rays entering the. photo-electric cell are rapidly interrupted as each opening in the belt or disk passes across the ruled screen or grating, giving rise to a pulsating current through the photo-electric cell, the amplitude of the current being controlled by the high lights and' shadows of the picture or view being transmitted. Fig. 17 shows the arrangement of the screen 189 with respect to the apron '5 and the tube 3.

In illustrating thevarious forms of my invention, I have sought to show the mechanism only a diagrammatic manner and have accordingly made no attempt to show the various parts in their propenrelative proportions. Moreover, I do not wish to be limited to the particular forms shown and described as it will be apparent that other modifications thereinmay be made without departing from the scope of my invention as set forth in the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is:-

1.. A picture transmission apparatus comprising means for producing an image of the picture tube transmitted, a belt having a J r series of small openings therein arranged to be'moved across the image, means for causing said belt tomove in a longitudinal direction and to slowly advance in a transverse direction, a photo-electric cell arranged to be controlled by light rays passing through said openings, and means for rapidly interrupting the transmission of light to said cell. 2. A picture transmission apparatus comprising means for producing an image of the picture to be transmitted, a photo-electric devlce arranged to be afiected by said image, a "screen havlng a series of spaced openings arranged in front of the cell means for moving the screen in one direction to cause theof said image, a continuous screen member arranged in front of said device and-having a series of spaced openings arranged in a. straight line through which light may pass from the image to the device, means for causing thescreen to move across the image in the direction of the line of said openings and means for causing the screen simultaneously to advance in a direction substantially at right angles thereto.

4. A pict-uretransmission apparatus comprising means for producing an image of the picture to be transmitted, a photo-electric device, a movable endless screen arranged with one portion between the image and the device and having a continuous straight line of spacedopenlngs therein, and means for causing said portion of'the screen to move in a direction making a small angle with the line of openings. I

5. A picture transmission apparatus comprising means for producing an image of the picture to be transmitted, a photo-electric cell arranged to be afi'ected by the light of said image, a belt having a series of spaced openings therein arranged to pass in front of the photo-electric cell, and means for causing the belt to move in a combined longitudinal and transverse direction whereby the successive openings in the-belt pass across the image in separate parallelvpaths.

In witness whereof, I have hereunto set my hand this 22nd day of September, 1924. CHARLES A. HOXIE. 

